Of all the lights you may know about on your dashboard, most drivers are aware of the Check Engine Light.
However, one light that isn’t as well known – the transmission warning light or transmission symbol – it certainly is not any less important.
What does the transmission warning light mean, and what causes the transmission warning light to come on? If you see the alert for your transmission on the dash, you need to take action.
I break down the meaning of the transmission warning light, what causes it, and show you how to fix it for a better ride. Plus, does this guide also answer if you should keep driving with this alert on the dashboard.
What is the Transmission Warning Light?
If the light for a transmission warning comes on, there is an issue with the transmission or gearbox.
Not every vehicle is equipped with a transmission warning light. If your vehicle does have one of these alerts, it may look different based on make and model.
The alert is either a thermometer and gear or a text string to inform you that you have a problem.
You should refer to your owner’s manual for specifics for your model. In any event, if you get a dashboard alert concerning the transmission, you have a fault and it should be looked into as soon as possible.
How to Diagnose the Transmission Warning Light?
#1. Stop Driving and Inspect.
If the Check Engine light comes on, you should stop driving right away, and you should also do the same when the transmission warning light comes on.
Even if you don’t notice any signs of an issue with the transmission, you still want to do a full inspection. If you don’t, you may do permanent damage to the transmission.
For example, if the system is low on fluid and you keep driving, you may need a new transmission instead of just putting it full back of fluid.
#2. Check for Trouble Codes.
Using a compatible OBD-II code scanner, you will be able to see what alarms are stored in the system. To read Diagnostic Trouble Codes (DTCs), plug the code scanner into the OBD-II port of the vehicle and see what the codes are.
If you see a lot of codes, you will want to clear them and take the vehicle for a test drive. After a few minutes the light should be back on, and you should be able to retrieve any relevant codes associated with that problem.
#3. Grab a Mechanic.
If the DTCs aren’t helpful in repairing the problem, it’s better to get a mechanic’s opinion. When you call, be prepared to state any oddity you see at the moment including the DTC as well.
It’s better to take the vehicle to a shop that sees transmissions in daily if you are worried that you may have a large issue requiring a transmission rebuild or replacement.
Causes of the Transmission Warning Light
#1. Low Transmission Fluid.
When the transmission fluid is low, this warning light may come on just because it’s warning you to prevent damage to the transmission. The transmission also won’t operate appropriately when the fluid is low.
Keep in mind that your car is not supposed to be burning through transmission fluid like engine oil. Therefore, in the case of low transmission fluid, take immediate action while you can to stop a leak from worsening.
#2. Overheating Transmission.
If the transmission is overheating for either low fluid or a mechanical failure inside the transmission, the warning light will come on. In some cases, a blocked cooler could be causing the overheating.
It could also overheat because you are carrying far too heavy of a load. Either way, it should be treated just like an engine overheating. You should STOP driving immediately and allow the transmission to cool off.
#3. Shift Interlock Failure.
There are times where the transmission warning light doesn’t actually indicate a failure with the transmission itself, but that a failure is occurring with a component working with the entire powertrain.
For instance, when asked to ensure the shift interlock system on BMW models that keeps you from being able to shift from Park unless your foot is pressing down the brake pedal. If that component fails, the transmission warning light may turn on.
#4. Malfunctioning Valve Body.
The automatic transmission and CVTs use a valve body, which contains valves to direct flow through the passages, so that flow gets sent to the transmission when needed.
The modern valve body will also include electronic components for the transmission control module (TCM), which controls all of the sensors and electronics. If any of these valve body components fail, the transmission warning light might come on.
#5. Failing Torque Converter.
The automatic transmission also has a torque converter which pairs the engine with the transmission that serves as a linking component.
With too much use or old age, the torque converter can wear out. When this happens, gear slippage with shuddering will occur.
The torque converter can also break apart and lead to contamination of the transmission system with debris. Any way you look at it, a failing torque converter is going to light the transmission warning light.
#6. Internal Transmission Failure.
There are many internal components that need to work, and it is possible for any of them to fail. Inside the transmission, you will find gear sets, clutch packs and much more.
With any internal failure, the transmission will not be able to work as designed or intended. This is what makes turning on the transmission warning light.
#7. Electrical/Computer Failure.
The modern transmission is powered by electrical connections and numerous sensors. While the transmission control module runs all the sensors accurately and creatively, any of these electrical connectors and sensors can fail at any time.
If anything is even the slightest bit wrong, with a glitch in the electrical system, the transmission may not work as it should. For this reason, it is possible for damaged electrical wiring, computer failure and a failing solenoid to all turn on the transmission warning light.
Is It Safe to Drive with Your Transmission Warning Light On?
I’ve mentioned this before but I will say it again – You Should NOT Drive with The Transmission Warning Light On.
Your car’s transmission is one of the most expensive components of the entire vehicle and, for that reason alone, you cannot afford to mess around with any faults that could permanently damage it.
Let’s say you stop driving with the light on only to realize it may actually just be a minor issue like a little leak. If that’s the case, you can fill it up and go to keep driving while keeping an eye on the issue.
If, however, there was a transmission overheating or an internal failure, you may feel like you just wasted a trip to your shop for nothing. While you could choose to ignore a small leak temporarily, again, it could escalate to a worse case at any moment.
These simple reasons are why most probably should go to the shop instead of just letting it go for the day or the week, it’s better to take care of the problem and prevent a future problem with the transmission occurring.
If ultimately there is a serious defect with your transmission you risk being stuck on the side of the road far from a mechanic or paying potentially $1500-$3500 or more for a transmission replacement.